1. Field of the Invention
This invention is directed to lightweight battery constructions where the current collector and carrier of the electrodes is of carbon fibre material.
2. Description of the Prior Art
The desirability of decreasing the weight and increasing the efficiency of batteries has long been a goal of battery designers. In obtaining that goal many considerations are involved, such as light weight, strength, current carrying capability and the lack of reactance with the active materials that form the battery. In lead-acid batteries, for example, a typical automotive battery can weigh 21.3 kilograms, with the current collector and carriers accounting for 5 kilograms or 23.5% of the total weight. The grids which make up the plates or electrodes of a typical lead acid battery, are usually of mesh configuration, and cast of lead and an alloy such as antimony. The finished grids have a paste of a lead oxide (in powdered form) and dilute sulfuric acid applied thereto which is then dried to form finished plates.
The finished grids serve both as a support for the active material on the plates and conduct the electric current. The grids also help to maintain uniform current distribution throughout the mass of active material.
The grids are subjected to considerable stress during charging and recharging which can result in their buckling, or separating from the pasted active material, resulting in a loss of efficiency and shortened service life.
It is highly important that the grids be free from inpurities which is often difficult to accomplish and which reduces efficiency of the battery due to improper banding or reactance with the active material.
Other batteries such as alkaline metal or alkaline earth metal batteries are in wide use and are desired for many applications.
As is known, while alkaline metals and alkaline earth metals are highly reactive, they are particularly suitable for use in batteries due to their ionic and electrical properties.
Of the alkaline metal or alkaline earth metals, lithium has been found particularly suitable for incorporation into batteries, but due to its inherent characteristics, lithium requires careful handling and special application treatment.
The alkaline metal or alkaline earth metals used are usually bounded or coated onto current collecting and carrying bases of metal foil such as copper, nickel or aluminum. The alkaline metals used include lithium, sodium, potassium and cesium with lithium being the material of choice. The alkaline earth metals would include beryllium, magnesium, calcium, strontium and barium. It has been observed that while alkaline metals, such as lithium, may initially appear to not react with copper or other metal foil bases, over a period of time the alkaline metals often react unfavorably with the metal foil base, and form an alloy with the metal, which results in decreased efficiency and a shorter than desired shelf and/or service life. It is important that the metal foil be free from impurities but this is difficult to accomplish and it has been found that the alkaline metal may react with even very minute amounts of impurities associated with the foil and which are difficult to remove.
It should also be noted that the base metal foils in alkaline batteries account for even more of the total battery weight than lead acid batteries and as much as 50% of the total battery weight. Weight reduction is desirable and will increase the energy density and reduce the cost of the battery. Examples of prior art alkaline or alkaline earth metal electrochemical cells, batteries and components are described in the article by Hooper, et al. in Advanced Battery Development, Odense University Press, 1984 and in the U.S. Patents to Andre et al., No. 4,357,401, Bannister, No. 4,471,037, Sugiuchi et al., No. 4,496,638, Skotheim, No. 4,520,086, and Hope, et al., No. 4,576,883.
The current collector and carrier of the invention provides batteries that do not suffer from the disadvantages of prior art batteries, and which provide many positive advantages.